The present invention relates to an electric motor and more particularly to brush gear for an electric motor.
Brush gear in small electric motors, particular fractional horsepower permanent magnet direct current (PMDC) motors, typically comprises a carbon brush which is carried on an end of a resilient, electrically conducting armxe2x80x94the brushleaf. The brushleaf is arranged to bias the brush against a commutator on the motor shaft. Typically the brush gear is mounted in an end cap which carries a bearing for the motor shaft and forms a structural part of the motor assembly.
In low voltage applications, the total resistance of the motor becomes more and more determined by the interface resistance between the brushes and the commutator. As the motor resistance determines the maximum power range within which the motor can operate, reducing the brush/commutator interface resistance is very desirable.
According to the invention there is provided an electric motor brush assembly comprising resilient electrically conductive support means arranged to carry two or more separately formed brush bodies axially displaced with respect to a longitudinal axis of the motor and connected electrically in parallel.
The support means normally comprises a separate arm for each brush body.
The separate arms may be arranged to have different natural resonance frequencies of oscillation.
The brush bodies may have different sizes and/or different physical densities.
A fractional horsepower direct current electric motor may be provided having a brush assembly comprising resilient electrically conductive support means arranged to carry two or more separately formed brush bodies axially displaced with respect to a longitudinal axis of the motor and connected electrically in parallel.